用迈克尔逊干涉仪测薄膜厚度

在教材中,常可见到“把折射率为n的薄膜放在迈克尔逊干涉仪的一臂上,由此干涉条纹产生移动,测得共移动N条,若光源的波长为λ,求薄膜的厚度”的习题。实际上由于薄膜的引入,导致干涉条纹的移动是个突变过程,无法测出干涉条纹移动的条数N。但这并非说不能利用迈克尔逊干涉仪测量薄膜的厚度,利用迈克尔逊干涉仪不仅可以测量透明介质膜的厚度,而且还可测量金属膜的厚度,下面介绍利用迈克尔逊干涉仪测量非透明金属膜厚度的原理及方     

用迈克尔逊干涉仪测量单层薄膜的厚度和折射率

薄膜厚度的测量是薄膜科学的重要分支之一，本文讨论用迈克尔逊干涉仪观察白光等厚彩色干涉条纹方法，从而确定薄膜的厚度和折射率，该方法的优点是测量精度高，原理简单，在一次测量过程中可同时确定薄膜的厚度和折射率。     

基于改进的迈克尔逊干涉仪的液体折射率测量方法研究

液体折射率是重要光学参数之一，液体折射率参数测量在食品生产鉴定、光学加工等领域都具有重要意义。本文基于便携式迈克尔逊干涉仪，在光学减震台上加装旋转微调载物台，综合考虑旋转后容器器壁、待测液体、空气中光程差的改变量，得到液体折射率的计算公式，与阿贝折射仪测量液体折射率的值进行比较，实验测得水、不同浓度的葡萄糖溶液以及不同浓度的氯化钠溶液，平均相对误差分别为1.1%、3.3%、2.0%,实验过程中测量的最大误差为5.9%,为液体折射率测量提供了一种可行方法，实现液体折射率的测量。本文也可作为迈克尔逊干涉仪的拓展实验，对本科生的创新能力培养有重要意义。     

改进型迈克尔逊干涉仪测量溶液折射率

将传统的迈克尔逊干涉仪进行改装并用于蔗糖溶液折射率的测量，装置采用OpenMV摄像头进行干涉条纹的识别，减速电机加步进电机进行位移测量，Arduino单片机进行控制和运算。改装后的迈克尔逊干涉仪有效缓解了操作过程中的视觉疲劳，减少了读数误差和测量误差。实验结果表明，所测折射率数据准确，与理论计算结果吻合。该装置可以广泛应用于大学物理实验，也为进一步工业化应用提供了可行性。     

迈克尔逊干涉仪测透明介质厚度及折射率

提出了使用用迈克尔逊干涉仪,改变光源入射方式及观测方式以获得稳定、清晰等厚干涉现象的方法.探究了在光路中插入的被测透明介质如何对等厚干涉条纹产生影响,并导出了被测介质厚度、折射率及旋转角度与等厚干涉条纹移动量之间的关系.实现对透明介质厚度、折射率进行简练、快速的同时测量.     

基于数字全息技术的迈克尔逊干涉仪设计与应用

传统的迈克尔逊干涉仪只能简单地呈现光的干涉图像,并不能生动体现光的波动特性及其形貌特征,且测量过程繁琐。针对这些问题,提出了一种基于数字全息技术的新型迈克尔逊干涉仪实验装置。该装置采用2个CCD相机代替传统迈克尔逊干涉仪中的平面反射镜,并引入与球面光相干的平面参考光与球面光发生干涉,利用数字全息技术直接获取2个CCD记录面上的球面光复振幅信息,然后通过最小二乘拟合获取球面波参数,并对球面光复振幅进行解调得到居中后的球面光复振幅,最后通过数字干涉的方法实现两球面光的干涉。实验结果表明,该装置能实时生动地显示入射球面光的三维图像和两球面光的干涉图像,同时根据拟合得到的参数能便捷地测量透明等厚介质的折射率,实验中测量了3种不同材料的折射率,其误差均能控制在±5%以内,有较高的测量精度。     

薄SiO_2膜厚度的椭偏测量方法

应用常规椭偏方法测量膜厚小于 ３００Ａ的薄ＳｉＯ２膜厚度时，由于膜的折射率对已知参数比较敏感，因而测量误差较大．本文给出一种薄ＳｉＯ２膜厚度的椭偏测量方法，引入等效入射角的概念，用曲线拟合求交点的办法精确确定了膜的折射率和厚度．     

厚度误差对THz-TDS的测量不确定度分析

阐述了基于菲涅尔公式的透射式太赫兹时域光谱系统提取样品光学常数的方法和原理,分析了样品厚度误差对THz-TDS测量不确定度的影响,并建立了相应的不确定度模型。进行太赫兹时域光谱测量实验,提取硅片在太赫兹波段的折射率,并计算了误差对提取样品折射率的影响。结果表明,随着厚度误差的增大,系统测量偏差也随之增大。对于较厚样品,相同厚度误差对其测量结果影响较小。样品厚度为994μm时,在厚度存在1μm的测量误差情况下,系统测量折射率的偏差为0.001 2,接近模型的仿真值。实验结果验证了厚度误差对测量不确定度模型的有效性,了解了厚度误差对系统测量结果的影响情况,对测量过程及结果分析具有一定的指导意义。     

基于折射率调制的表面等离子体全息衍射效率分析

针对折射率调制的表面等离子体全息显示方案,采用严格耦合波计算方法,仿真了变折射率薄膜正弦光栅结构参数与衍射效率的关系.结果表明,银作为表面等离子体激发材料时,0.2μm为光栅最优厚度,在此基础上,一级次光衍射效率与折射率差值、周期呈正比增长关系.对折射率范围进行了拓展,确定了折射率调制范围在1.34～1.8、周期为0.9μm时,对应的衍射效率可达33%以上.研究结果对于优化设计表面等离子体全息显示结构具有参考意义.     

用迈克耳逊干涉仪测量气体折射率的误差的研究

研究在用迈克尔逊干涉仪测量气体折射率时存在的系统和方法误差，提出了误差修正方法。     

迈克耳孙干涉仪应用功能的扩展

通过对迈克耳孙干涉仪的简易改装,实现了光速测量、透明固体和液体的折射率测量、金属丝弹性模量测量以及多普勒效应的演示,拓展了迈克耳孙干涉仪的应用功能.     

Direct measurement of dispersion of the group refractive indices of quartz crystal by white-light spectral interferometry

We present a white-light spectral interferometric technique employing a low-resolution spectrometer for a direct measurement of the dispersion of the ordinary and extraordinary group refractive indices of a quartz crystal over the wavelength range approximately from 480 to 860 nm. The technique utilizes a dispersive Michelson interferometer with the quartz crystal of known thickness to record a series of spectral interferograms and to measure the equalization wavelength as a function of the displacement of the interferometer mirror from the reference position, which corresponds to a balanced non-dispersive Michelson interferometer. We confirm that the measured group dispersion agrees well with that described by the dispersion equation proposed by Ghosh. We also show that the measured mirror displacement depends, in accordance with the theory, linearly on the theoretical group refractive index and that the slope of the corresponding straight line gives precisely the thickness of the quartz crystal.     

Optical refractometer based on an asymmetrical twin-core fiber Michelson interferometer

We report and demonstrate an optical refractometer based on a compact fiber Michelson interferometer. The Michelson interferometer is composed of an asymmetrical twin-core fiber containing a central core and a side core. By chemically etching a segment of the twin-core fiber until the side core is exposed, the effective index of the side core in the etched region is sensitive to the environmental refractive index, which leads to a shift of the transmission spectrum of the Michelson interferometer. The experimental results show that such a device has a refractive index resolution of more than 800 nm/refractive index unit in the range of 1.34-1.37.     

真空蒸发镀膜膜厚的测量

测量镀膜厚度的方法有很多,在实验室现有的条件下,探究光学干涉方法测出镀膜厚度,其中光学干涉方法包括两种：一是根据多光束干涉的原理,利用读数显微镜测量镀膜的厚度;二是根据自光干涉的原理,利用迈克尔逊干涉仪测量镀膜的厚度。     

A spectral interferometric method to measure thickness with large range

We present a spectral interferometric method to measure the thickness of an optical plate or a film with a single layer. The system is based on the Michelson interferometer configuration, and the spectral interference signal of a broadband light source is recorded by a spectrometer. The optical path difference (OPD) between two interfering beams can be obtained by Fourier transform from the spectral interferogram. Gaussian fitting is used to find the exact peak of fringe to enhance the precision of the measurements. When the sample is inserted into the sample beam, the film’s thickness can be calculated by comparing the change of OPD, provided that the sample group refractive index is known. Only a single measurement is needed to determine a film’s thickness after the initial OPD of the system is calibrated. As no moving parts are required, the system has good stability. In particular, a large range of thicknesses, from micrometers up to several millimeters, can be measured. Such a large range is valuable for optical measurements. For demonstration, we measured the thicknesses of preservative film, cover glass and carrier glass, which were 9.6 ± 0.55, 156.1 ± 0.75, 1008.44 ± 0.96 μm, respectively.     

Direct measurement of group dispersion of optical components using white-light spectral interferometry

We present a simple white-light spectral interferometric technique employing a low-resolution spectrometer for a direct measurement of the group dispersion of optical components over a wide wavelength range. The technique utilizes an unbalanced Mach-Zehnder interferometer with a component under test inserted in one arm and the other arm with adjustable path length. We record a series of spectral interferograms to measure the equalization wavelength as a function of the path length difference. We measure the absolute group refractive index as a function of wavelength for a quartz crystal of known thickness and the relative one for optical fiber. In the latter case we use a microscope objective in front and a lens behind the fiber and subtract their group dispersion, which is measured by a technique of tandem interferometry including also a Michelson interferometer.     

利用迈克尔逊干涉仪制备全息光栅

利用迈克尔逊干涉仪上调节出的等厚干涉条纹,将全息干版放置在观察屏处曝光,经过处理后得到全息光栅,利用分光计测出光栅常数.     

近红外波段锑基铋掺杂薄膜厚度对光学常数与光学带隙的影响

采用磁控溅射法制备了不同厚度的锑基铋掺杂薄膜,用X射线衍射(XRD)和透射电子显微镜(TEM)研究了薄膜结构随厚度的变化。利用椭圆偏振法测定了样品薄膜在近红外波段的光学常数与光学带隙,研究了膜厚对样品薄膜光学常数和光学带隙的影响。结果表明,膜厚从7 nm增加至100 nm时,其结构由非晶态转变为晶态。在950～2200 nm波段,不同厚度薄膜样品的折射率在4.6～8.9范围,消光系数在0.6～5.8范围,光学带隙在0.32～0.16 eV范围。随着膜厚的增加,薄膜的折射率和光学带隙减小,而消光系数升高;光学常数在膜厚50 nm时存在临界值,其原因是临界值前后薄膜微观结构变化不同。     

The effect of surface roughness on fringe visibility in optical interferometry

A review of theoretical results expressing the fringe visibility as a function of the r.m.s. surface roughness of the test piece for several types of interferometer is presented. Michelson, Fresnel mirror, shearing, holographic, and dual wavelength holographic interferometers are considered. The results for each of these arrangements are compared in terms of a common variable, that is the effective wavelength or contour separation. Results compare well in most cases considered.

The preliminary calibration of the visibility of contour fringes observed in a dual index holographic interferometer with respect to the surface roughness of the object is also described. This experiment demonstrates that, following a more extensive calibration, surface roughness over a very wide range can be measured using the latter technique.

The authors' main interest in these techniques is related to the simultaneous measurement of wear and surface roughness. A demonstration example of this type of measurement is also shown.